Can anyone with experience tell me what it is like to edit
in D-VHS-ie copying segments here and there to a second tape
(as opposed to just copying a whole tape). Is this possible
or does interrupting the bitstream by making a cut make
editing impossible?

Don Landis

06-15-2000 12:02 AM

Traditional assemble editing in an analog fashion is not possible with the digital recording methods on the PVHD1000. My attempts at this from different channel sources at different times indicate a momentary gap or screen to black for a few seconds as the playback locks onto the next program on the tape. This is similar to what happened in the first VHS VCR's back in the late 70's before back space assemble editing was added to nearly all VCRs when using the pause button during recording. Additionally, I don't see how it is possible without additional hardware to see what you are doing when making a simple tape to tape dub since you will be using the only IEEE1394 ports when connecting two DVHS PVHD1000's for this purpose.
I had asked Richard Adams this very same question as he has two DVHS machines and has some hands on experience with this process. I am waiting for his reply. Richard?

I think the assemble editing in DV and DVCPRO camcorders have better assemble editing capability than the PVHD1000. Essentially, the PVHD1000's only feature worth noting is that it is capable of simple recording of HDTV bandwidth programs from the Dish5000/HDTV monitor and any OTA through the DST5x tuner.

Don-thanks. Another industry professional told me that
the W-VHS format is a lot better for editing, it is
analog HD. Also, it can record from any source, using
any STB since it records the RGB output. But it is does
not have Dolby Digital, and it sacrifes some of the
Luma (I think) in HD- in other words it is not quite
as good but may be better for editing.

Don Landis

06-17-2000 10:05 AM

Marv:

Keep in mind that while the W VHS system is analog and will not do DD it is pricey and it is still not an edit VCR. I don't know what your real plan is for editing HDTV but I don't think there is any cost effective solution yet for any editing as we know it. In the future, look to Non linear edit systems in a computer/hard drive for real HDTV editing. It will be far cheaper, simpler, and easier to edit this way than old fashion linear tape to tape or signal to tape HDTV editing.

The PV-HD1000 seems to lack a flying erase head. This is what makes for glitch free edit cuts. Lacking the flying erase head and accurate repositioning of the tape, it is extremely difficult to apply this machine for even simple linear editing.

Don Landis

06-18-2000 11:05 AM

Richard:

I did some testing last evening with a tape that was pre-stripped, ie. laid down a digital video signal end to end. Then I went back and recorded a program that I terminated at an exact time on the control code clock. Then I went to a different source and began the tape at that moment in time. While it was not perfect, it appears that a glitch at the edit points may be eliminated by having a tape that was previously recorded end to end. In this way if you begin the next assemble edit just beyond the end of the previous program you won't lose digital bitstream that will cause the picture to be lost or go to a digital breakup before locking onto the next program.

Actual measured times for the edits are:

Recovered picture using simple pause edit during record less than a second of pixel collapse before new solid picture and sound even when editing between a 4:3 picture in a 16X9 HD and a 16X9 HD frame size.
Recovered picture where the tape is started without a prestripe under bed of black between edits. 7 seconds consisting of 3 seconds of last picture still, then collapse and black for 4 seconds then new picture.
Recovered time when new edit occurs with a black prestripe underbed is less than a second as the video cuts to black with a moment of pixel collapse and the picture returning to next program with a flash of black between.

While no edit is glitch free the time of using an underbed of black and/or using the pause during a record session is far less than when an edit is performed while allowing the recording to go to blank tape before the next program start.

The PVHD1000 appears to not* do back space edits on assemble so, having the digital black prestripped will allow the video to either switch directly to the new program with a non-frame accurate cut or it will cut to black on the background and then cut to the new program. Either way is an improvement over attempting to assemble edit to a truly blank tape that may skip some inches of tape with no recording, no control track, and cause a long time to lock up on the new recording. Keep in mind this is still assemble editing and it still can only be done from tape beginning to tape end. You still cannot go back and do an insert edit which does require the rotary erase head and frame accurate positioning.

*back space editing is required to prevent the control track code from being different at each edit which causes the drum servo to change speed at the edit points. I need to perform more testing to see if this machine does do a back space positioning to prevent the control code discontinuity. If it does then it may be possible to do assemble editing in one pass but not without loosing some of the previously recorded program each time. Tape positioning is still a key factor which the PVHD1000 is not designed to do well at all.

The control code time counter is fairly accurate but it requires a zero set point to be repeatable. Knowing where to reset the counter is most of the battle with getting this time to be any more repeatable than within a few seconds.